Method of producing artificial threads



Patented Mar. 6, 1934 UNITED STATES PATENT OFFICE METHOD OF PRODUCINGARTIFICIAL THREADS No Drawing. Application December 10, 1930, Serial No.501,473

.5 Claims.

This invention relates to regenerated cellulose structures produced bythe viscose method and in one of its specific embodiments relates to theproduction of threads having increased tensile strength both in the wetand dry states.

According to the common practice of producing artificial threads by theviscose method, a viscose solution prepared from cellulose Xanthatedwith about 35% of carbon bisulphide,

based on the weight of the cellulose, is spun in a coagulating bath. Ifthe coagulating bath is an acid one, it usually contains from about 8%to 20% of an acid, such as sulphuric. The threads resulting from such aprocess possess a dry tenacity of approximately 1.50 grams per denierand a wet tenacity of approximately 0.70 grams per denier. As isapparent, these tensile strengths are relatively low and many attemptshave been made to improve them. One of the methods devised to producethreads of increased tensile strength consisted of spinning a viscosesolution, produced in the usual manner, in an acid bath containing 50%or more of sulphuric acid whereby the threads were rendered capable ofbeing stretched to an increased extent. Another method contemplatedreducing the amount at alkali in the viscose to about 5% and spinningsuch a viscose into an acid bath contamin sulphuric acid.

l have found that other changes in the nature of the viscose and in theprocess used in the preparation thereof have a controlling effect on theconcentrations or" acid which should be used in the bath and on thetensile strength of the threads produced. More particularly I have foundthat the amount of carbon bisulphide used in the xanthation has a markedefiect on the amount of acid which should be used in the spinning bathto give threads of very high tensile strength. Specifically, I havefound that, when less than 25% of carbon bisulphide is used in thexanthation and the viscose produced therefrom spun in an acid bathcontaining sulphuric acid, not in excess of threads having greatlyincreased tensile strength, both wet and dry, are produced.

It is therefore an object of this invention to provide a method ofproducing artificial threads by the viscose process having increasedtensile strength, both in the dry and wet states.

Another object of this invention is to provide a method of producingartificial threads by the viscose process having relatively high tensilestrength, wherein not more than 25% of carbon bisulphide, based on theweight of the cellulose, is employed in the xanthation.

A further object of this invention is to provide a method of preparingartificial threads having increased tensile strength which comprisesspinhing a viscose solution produced from cellulose xanthated with notmore than 25%, and preferably 17%, of carbon bisulphide, based on theweight of the cellulose, in an acid bath containing less than 50% andpreferably from over 40% to 47% of sulphuric acid.

Other objects will appear from the following description and appendedclaims.

Essentially this invention comprises spinning a viscose solutionprepared from cellulose xanthated with a relatively small quantity ofcarbon bisulphide in a bath containing a relatively high concentrationof acid. The amount of carbon bisulphide employed in the xanthation stepdoes not exceed 25%, and is preferably not less than 10%, by weightbased on the cellulose. The bath into which this viscose solution isspun has an acid concentration of less than 50%, and preferably fromover 40% to 47%, of a mineral acid such as sulphuric. The bath traveland the rate of spinning may vary within wide limits depending interalia on the concentration of the acid and/or the quantity of bisulphideused in the xanthation.

In order to more clearly define and explain this invention, thefollowing specific examples are set forth,

Example 11-100 parts of wood pulp of good grade employed for rayon, andpreferably a material having a high alpha cellulose content, andcontaining 6% or 7% of moisture are steeped in a caustic soda solutionof 17% to 20% strength at about 18 C. for 1 to 3 hours. The mass is thenpressed until the press-weight of the wet alkali cellulose is about 300to 320 pounds. After it has been shredded and aged at 20 C. for anysuitable length of time, such as 50 or 60 hours, the aged alkalicellulose is xanthated according to any well-known manner at anysuitable temperature, for instance 25 C., for approximately 2 to 3 hoursusing 1'7 parts of carbon bisulphide to parts of cellulose. Theresulting cellulose xanthate is formed into a viscose solution bydissolving it in a caustic soda solution at 18 C., the quantity ofcaustic soda being such that the viscose solution contains 7% ofcellulose and 8% of alkali calculated as NaOI-l. The solution thusproduced is filtered and then ripened for 12 to 20 hours atapproximately 18 C. After ripening, the solution is finally spun into abath n containing 45%-50% of acids and preferably 47% sulphuric acidmaintained at approximately 10 C.

A thread of 2.5 deniers per filament has been successfully produced whenthe pump delivery was 10 grams of viscose per minute and the viscose wasforced through spinnerets having 40 orifices or holes, each 0.0035 inchin diameter, the thread having a bath travel of from 20 to 30 inches anda take-up speed of 3,000 inches per minute.

Suitable moderate tension secured in any of the well-known ways isapplied to the threads during their travel in the bath. The coagulatedand regenerated threads, after passing through the acid bath, aretreated in any suitable manner to arrest the action of the acid. Forexample, the coagulated and regenerated threads are passed from the acidbath into a bath containing water, in which additional tension may beapplied to the partially washed threads. The threads are thenaccumulated in or on a collection device which may also be treated withsuitable washing liquid. Y

Example II.-100 parts of cotton linters containing 5% to 6% of moistureare steeped in a caustic soda solution of 17% to 20% strength at about18 C. for 1 to 3 hours. The mass is then pressed until the press weightof the Wet alkali cellulose is about 310 to 330 lbs. After it has beenshredded and aged at 20 for to hours, the aged alkali cellulose isXanthated according to any well-known manner at any suitabletemperature, for instance 25 C. for approximately 2 to 3 hours using 21parts of carbon bisulphide to 100 parts of cellulose. The resultingcellulose xanthate is formed into a viscose solution by dissolving itinto a caustic soda solution at 18, the quantity of caustic soda beingsuch that the viscose solution contains 7% of cellulose and 8% of alkalicalculated as NaOH. The solution thus produced is filtered and ripenedfor 5 to 10 hours at approximately 18. After ripening, the solution isfinally spun into a bath containing 42% sulphuric acid and 15% aceticacid at 10 C.

The spinning conditions are the same as previously described underExample vI:

The use of acetic acid in combination with the sulphuric acid permitsthe use of lower concentrations of sulphuric acid without losing theeffectiveness of a greater concentration of sulphuric acid.

Example III.-Aged alkali cellulose, prepared from high grade wood pulpas set forth in Example I, is Xanthated with 14 parts of carbonbisulphide to 100 parts of cellulose as described in the aforementionedExample I. A viscose solution is then prepared as in Example I. Afterripening, the solution is spun in a bath at approximately 10 C.containing 44% of sulphuric acid saturated with sodium sulphate. Thethread is further treated as set forth in Example I.

It is evident that certain changes can be made in the above exampleswithout departing from the spirit of the invention. For example, asuitable grade of cotton linters or other source of cellulose may beused in place of the wood pulp which has been specifically mentioned.The time of aging of the alkali cellulose is subject to some change butwill preferably tend to be for a rather long period in view of therelatively small amount of carbon bisulphide used. The percentage of thecellulose in the viscose may also be varied over the ranges which arenormally used in this art, and this invention is not to be restricted tothe precise percentage of cellulose which is disclosed in the specificexamples. The coagulating bath within the range which has been describedmay be modified by the addition of any of the well-known materials whichare customarily used in coagulating baths, such as inorganic sulphate,glucose and the like. There may also be used with the sulphuric acideither in the presence or absence of the inorganic sulphate such organicacids as acetic acid, which permits the use of smaller quantities ofsulphuric acid while still retaining the effectiveness of higherquantities.

The threads produced according to this method have a vdry tenacity of atleast 3 grams per denier and a wet tenacity of at least 1.8 grams perdenier.

By the term cellulose as used in this specification and claims is meantthe total material in the viscose recoverable as film or thread bycoagulation in an acid bath followed by washing and drying. i

Though the invention is specifically described above in the manufactureof artificial thread, the invention is not restricted thereto. It isequally applicable for the manufacture of any regenerated cellulosestructures including films.

Since it is obvious that various other changes may be made intheispecific details set forth above, this invention is not restrictedthereto except as set forth in the appended claims.

I claim:

1. The process of producing regenerated cellulose structures whichcomprises introducinga viscose solution containing 8% of alkalicalculated as NaOI-I prepared from a cellulose Xanthated with from 10%to 25% of carbon bisulphide, based on the weight of the cellulose, in abath containing from over 40% to less than 50% sulphuric acid.

2. The process of producing artificial threads of high tensile strengthwhich comprises spinning a viscose solution containing 8% of alkalicalculated as NaOH prepared from a cellulose xanthated with from 10% to25% carbon bisulphide, based on the weight of the cellulose, in a bathcontaining from over 40% to less than 50% sulphuric acid.

3. The process of producing artificial threads of high tensile strengthwhich comprises spinning a viscose solution containing 8% of alkalicalculated as NaOH prepared from a cellulose xanthated with 17% carbonbisulphide, based on the weight of the cellulose, in a bathcontaining47% sulphuric acid.

4. The process of producing artificial threads of high tensile strengthwhich comprises spinning a viscose solution containing 8% of alkalicalculated as NaOH prepared from a cellulose Xanthated with 21% ofcarbon bisulphide, based on the weight, of the cellulose, in a bathcontaining 42% sulphuric acid and 15% acetic acid.

5. The process of producing artificial threads of high tensile strengthwhich comprises spinning a viscose solution containing 8% of alkalicalculated as NaOH prepared from a cellulose xanthated with 14% carbonbisulphide, based on the weight of the cellulose, in a bath containlyingsodium sulphate and 44% sulphuric acid.

HAROLD HENRY PARKER.

